Based on the fact that this is your classroom tank, I will make the following comments.

Quote Originally Posted by Darth-Tater View Post
...sunpod MH 150 watts...
Hot, bright fixture just screaming "burn me." However, you would have a better light than stock.

Quote Originally Posted by Darth-Tater View Post
...a nova etreme or a 6x18 watt t5 fixture...
Can you find after market replacement bulbs in 18 watts? I looked at this fixture a while back myself. I'm definitely a T5 fan!

Quote Originally Posted by Darth-Tater View Post
...The last option is just replace the hood and ballast...
It would maintain the all in one look and keep hands out of the tank.

I guess your choice would depend on the students' personalities and ability to get into trouble, in your classroom.

For my first graders, I would keep the tank covered, no doubt.

Christopher